There are proposed several methods of controlling the growth of the single crystal for use in semiconductors or optical devices by monitoring the state of the growth of the single crystal by irradiating X rays thereto. In one example, Japanese Patent Publication No. 34440/1973 discloses that as shown in FIG. 1, characteristic X-rays 6 are projected through a slit 2 from an X-ray source 1 to a single crystal 3 which is rotated around the pulling up axis with a constant rotating speed, then the X-rays 7 diffracted from the crystal plane of the single crystal is measured by a counter device such as a proportional counter or a scintillation counter, so that the growth of the single crystal is monitored, thereby controlling the rotational speed of the single crystal, calibrating the growth direction or observing the state of the crystal such as a fault of the crystal. In FIG. 1, the reference numeral 4 is a furnace body such as a quartz crucible and 5 is a crystaline material to be grown to the single crystal.
However, this proposed method has a disadvantage that it is very difficult to recognize the correct crystaline state since detection of the diffracted X-rays by the counter due to difficulty in correct geometric setting of the X-ray source, crystal and counter. More specifically, since the characteristic X-ray source is used with a fine opening of the slit 2, the width of the diffracted X-rays is very small and therefore can only be detected in the reflection angle of 2.theta. and furthermore, since the crystal is rotated, the reflection of the X-ray from the crystal is interrupted, whereby the counter can not surely detect the diffracted X-rays partly because the direction of the reflection of the X-ray is changed corresponding to the change of the diameter of the grown crystal and the finder of the scintillation counter is relatively small. Furthermore, according to the proposed method, since only the traces of the Laue spots of the crystal plane can be observed, change of the diameter of the crystal pulled up can not be detected, whereby control of the diameter of the pulled crystal can not be made by only monitoring the output of the scintillation counter.
While the JOURNAL OF CRYSTAL GROWTH 310-212 (1974) proposes another way of monitoring of the crystal growth wherein an X-ray image amplifier is used to monitor the crystal in a two dimensional manner by irradiating the white X-rays onto the crystal which is in the pull up process. However, this proposed way is only possible to recognize the change in the shape of the crystal and is impossible to recognize the crystal characteristic such as twin crystal or multiple crystal.